Auto merge of #46288 - alexcrichton:bump-bootstrap, r=Mark-Simulacrum

Bump to 1.24.0

* Update the in-tree version number
* Update the bootstrap compiler
* Remove `cfg(stage0)` annotations
* Update crate dependencies
* Update Cargo itself

src/librustdoc/html/render.rs

@@ -34,8 +34,6 @@
 //! both occur before the crate is rendered.
 pub use self::ExternalLocation::*;
 
-#[cfg(stage0)]
-use std::ascii::AsciiExt;
 use std::borrow::Cow;
 use std::cell::RefCell;
 use std::cmp::Ordering;